Heretofore the mounting of a tubular instrument, e.g., a catheter, on a guide-wire has typically required access to either the distal or the proximal end of the guide-wire. Where the guide-wire is already in place, access has been achieved by mounting the instrument on the proximal end of the guide-wire and then sliding it into place over or along the guide-wire. For example, the so-called “over-the-wire” catheter (such as a balloon angioplasty catheter) has a central or other longitudinal extending passageway therethrough arranged to receive the guide-wire. In particular, the passageway of such a catheter is introduced on the proximal end of the guide-wire and then the catheter is slid down the guide-wire to the desired location. The advantage of this type of instrument and guidance system is that it can have a relatively small cross-sectional area or “crossing-diameter,” a feature of some importance in applications wherein the lumen being traversed is small, e.g., an artery occluded by atherosclerotic deposits. The so-called “mono-rail” catheter doesn't make use of a central passageway for receipt of the guide-wire, but instead makes use of some externally located connector located on the distal end of the catheter and arranged to receive the guide-wire through it. The mono-rail catheter is also arranged to be introduced on the proximal end of the guide-wire, but outside the guide-wire so that the guide-wire passes through the connector on the distal end of the catheter, with the catheter itself being located beside the guide-wire so that it can be slid along the guide-wire to the desired location.
As will be appreciated by those skilled in the art, if the proximal end of the guide-wire has some structure permanently or transiently mounted or secured on it, e.g., a twist or torque handle (for rotating the guide-wire to a desired angular orientation), a valve (to enable some gas to be introduced through the guide-wire, such as to inflate a balloon on the distal end of the guide-wire), another catheter, etc., that is of a relatively large diameter or cross-sectional area, such a proximally mounted structure would necessarily impede the mounting of the instrument over the guide-wire once the guide-wire is in place within the being's body.
In U.S. Pat. No. 6,022,336 (Zadno-Azis et al.) there is disclosed a catheter system for revascularizing an occluded vessel and for containing any emboli produced during the use of the system. As best seen in FIGS. 7 and 10A of that patent the instrument makes use of plural catheters for providing at least one pair of paths for irrigation and aspiration fluid flow. One of the catheters, designated as an “intermediate” catheter includes an externally mounted lumen structure for receipt of an inner catheter therethrough. This lumen structure may include a longitudinally extending slit or weakened area along the entire length of the lumen structure to facilitate faster and easier insertion and removal of the inner catheter through the side wall of the lumen structure. By inserting and removing the inner catheter through the slit in the side wall of the lumen structure, the need to remove adapters and attachments from the proximal end prior to slidably advancing or removing the intermediate catheter over the inner catheter is eliminated. Thus, this lumen structure which is mounted at the distal end of the intermediate catheter for accommodating the inner catheter enables the intermediate catheter to be guided along the inner catheter in a manner like the heretofore discussed mono-rail catheters are slid along a guide-wire. However, unlike the prior art devices for mounting an instrument on a guide-wire in a mono-rail like arrangement, the device of Zadno-Azizi et al. patent does not require access to the proximal end of the intermediate catheter or guide-wire. Instead the device of the Zadno-Azizi et al. patent enables the inner catheter to be inserted laterally into a longitudinally extending access slit in the lumen structure at a intermediate location along the inner catheter. By inserting and removing the inner catheter through the slit in the side wall of the lumen structure on the distal end of the intermediate catheter, the need to remove adapters and attachments from the proximal end of the intermediate catheter prior to slidably advancing or removing that catheter over the inner catheter is eliminated.
While the instrument of the Zadno-Azizi et al. patent appears generally suitable for its intended purposes, it appears to leave something to be desired from various standpoints. For example, since the lumen structure with the access slit is located externally to the intermediate catheter it will necessarily add its diameter to the diameter of the intermediate catheter, thereby limiting its usefulness to relatively large crossing diameter lumens. Also, the manner in which the intermediate catheter is attached or mounted onto the inner catheter or guide-wire may be somewhat difficult to achieve, and the additional structure, e.g., the slit bearing lumen structure, on the distal end could cause the distal end to get snagged on stents placed in the vessel. Further still, since the slit through which the inner catheter or guide-wire is inserted is linear and extends longitudinally, the inner catheter or guide-wire may come out of the lumen during the traversal of difficult anatomical orientations, e.g,. tortuous vascular paths.